1. Technical Field
The application relates to a semiconductor device and a fabricating method thereof, and more particularly to a nitride semiconductor template and a fabricating method thereof.
2. Description of Related Art
Currently, when a semi-polar nitride semiconductor (e.g. a gallium-nitride layer) is grown on a silicon substrate, the defect density in the gallium-nitride (GaN) layer is approximately between 108 cm−2 and 109 cm−2. Since the (0001) GaN multiple quantum well (MQW) layer has great spontaneous polarization field, the light-emitting efficiency thereof is deteriorated. On the contrary, since the semi-polar GaN MQW layer has lower spontaneous polarization field, the light-emitting efficiency thereof and the wavelength stability are favorable. In the prior arts, semi-polar GaN semiconductor is grown on a silicon substrate. Since lattice mismatch between the semi-polar GaN semiconductor and the silicon substrate exists, it is difficult to enhance epitaxial quality of the semi-polar GaN semiconductor. Moreover, since coefficient of thermal expansion (CTE) mismatch between the semi-polar GaN semiconductor and the silicon substrate is as high as about 54%, excessive stress accumulates and causes the semi-polar GaN semiconductor layer warped and cracked. Accordingly, the thickness of the semi-polar GaN semiconductor grown on the silicon substrate is limited.
Currently, how to fabricate GaN semiconductor thin films having excellent epitaxial quality as well as sufficient thickness and how to prevent the GaN semiconductor thin films from warping or cracking are important issues to one ordinary skilled in the art.